Allergic diseases are frequently seen in non-human mammalian patients, just as they are in humans. For example, equine allergy most often manifests either as cutaneous or respiratory disease. Urticaria (hives), while not life threatening, is a major cause of economic loss in the horse industry, due not only to treatment expenses, but also to the result of lost activity for show and race horses. Allergy that manifests as respiratory disease varies from rhinitis and bronchitis to chronic obstructive pulmonary disease (heaves) and systemic anaphylactic shock, the latter of which can be fatal. The lack of availability of reliable in vitro methods to detect the allergens causing disease in an individual patient has made diagnosis and treatment of allergic diseases in non-human mammals difficult.
Equine IgE has been studied by several investigators using an assay based on a polyclonal anti-IgE antibody. Halliwell reported that normal horses have 107 μg/ml of serum IgE, which is several times more than normal levels in humans (Halliwell R. E. and Hines, M. T., Eye Research, 4:1023-1031 (1985)). Such high levels of equine IgE are likely to be a result of multiple internal parasitic infections. These levels are not unlike those reported for the dog, a genus that is also commonly infested with gastrointestinal parasites (Halliwell R. E. W., Journal of Immunology, 110:422-430 (1973); Halliwell R. E. and Hines, M. T., Eye Research, 4:1023-1031 (1985); Swiderski, C. E., Veterinary Clinics of North America: Equine Practice, 16:131-151 (2000)).
Recently, the complete nucleotide and deduced amino acid sequence of IgE has been ascertained (Marti, E. et al., Journal of Veterinary Immunology and Immunopathology, 47:363-367 (1995); Navarro, P. et al., Journal of Molecular Immunology, 32:1-8 (1995); Watson, J. L. et al., Veterinary Allergy and Clinical Immunology, 5:135-142 (1997)). As a result of these studies, recombinant fusion proteins, corresponding to equine IgE heavy chain region CH3 and CH4, have been produced that react to equine IgE under various conditions (Marti, E. et al., Veterinary Immunology and Immunopathology, 59:253-270 (1997); Watson, J. L. et al., Veterinary Allergy and Clinical Immunology, 5:135-142 (1997)). However, conformational requirements such as natural folding of fusion proteins have made it difficult to generate polyclonal and monoclonal antibodies that recognize native equine IgE (Grioto-Wenk, M. E. et al., Journal of Veterinary Immunology and Immunopathology, 75:59-69 (2000)). A recombinant fusion protein consisting of parts of CH3 and CH4 has been used to raise polyclonal rabbit antibodies specific for equine IgE (Watson, J. L. et al., Veterinary Allergy and Clinical Immunology, 5:135-142 (1997)). However, the antiserum was able to recognize only the reduced/denatured and non-reduced/denatured IgE but not the native IgE. A similar protocol was used by Marti et. al with the use of recombinant fusion protein immunized chickens (Marti, E. et al., Veterinary Immunology and Immunopathology, 59:253-270 (1997)).
Due to the very low concentration of IgE in serum, purification of sufficient IgE for production of diagnostic reagents is difficult. Efficient and cost-effective methods for producing antibodies specific to IgE are lacking in the prior art. The present invention addresses these and other needs.